The increasing cost of oil and natural gas and this country's dependence on supplies of oil from foreign sources has resulted in it becoming more cost effective and more politically desirable to explore for oil and gas in areas that were not previously cost effective—particularly in ocean floor areas under thousands of feet of sea water. Such deep sea exploration and recovery of oil and gas and the future potential to explore for fresh water in undersea areas has increased the need for specialized equipment capable of remotely performing sub sea tasks using remotely operated vessels (ROVs) capable of performing tasks at sea floor locations that are thousands of feet under the sea at the extreme pressures encountered at such depths.
Remotely operated underwater vehicles (ROVs) are the common accepted name for tethered underwater robots in the offshore industry. ROVs are unmanned, maneuverable and operated by a person aboard a boat/ship or platform. They are linked by a tether (sometimes referred to as an umbilical cable), a group of cables that carry electrical power, video and data signals back and forth between the operator and the vehicle. High power applications will often use hydraulics in addition to electrical cabling. Most ROVs are equipped with at least a video camera and lights. Additional equipment and tools are commonly added to expand the vehicle's capabilities. These may include sonars, magnetometers, a still camera, a manipulator or cutting arm, water samplers. And instruments that measure water clarity, light penetration and temperature.
Conventional ROVs are constructed with a large floatation pack on top of a steel or alloy chassis, to provide the necessary buoyancy. Syntactic foam is often used for the flotation. A tool sled may be fitted at the bottom of the system and can accommodate a variety of sensors. By placing the light components on the top and the heavy components on the bottom, the overall system has a large separation between the center of buoyancy and the center of gravity, this provides stability and the stiffness to do work underwater.
Electrical cables may be run inside oil-filled tubing to protect them from corrosion in seawater. Thrusters are usually located in all three axes to provide full control. Cameras, lights and manipulators are on the front of the ROV or occasionally in the rear for assistance in maneuvering. An example of an ROV use underwater is disclosed in U.S. Pat. No. 5,927,901 ('901) where the ROV is used in a pipeline pigging operation. As described in the '901 patent, ROVs have been used sub-sea for extremely simple operations, such as opening of valves in pipelines to allow flow of a liquid or gas through a pipeline. The process and apparatus described herein provides for a fluid stream treating process to be carried out underwater, where such prior art treating processes were only used on land or on an above-sea platform.
One of the problems encountered in a deep sea oil and/or natural gas recovery operation is the cost of erecting a platform for processing the oil and/or gas recovered from the ocean floor. Construction of such platforms is extremely difficult and expensive, particularly when at a location far from shore. Another difficulty with off shore oil and/or gas exploration is that EPA regulations are very strict in allowing essentially no hydrocarbons or other contaminants to be released into the ocean water. These EPA regulations make it very difficult to recover hydrocarbons, e.g., oil and/or gas, from the ocean floor since the recovered hydrocarbons, at extreme ocean depths, contain water that quickly corrodes piping used to convey the recovered hydrocarbons up to a platform or shore processing location. In addition, any device deployed at great ocean depths is subjected to extreme pressures and cannot have any trapped gas inside, e.g., air, since at the pressure encountered under thousands of feet of ocean water, the vessel would implode. Further, the installed piping initially is treated with a variety of inorganic and organic chemicals, such as corrosion inhibitors, scale inhibitors, and preservation fluids to prevent bacteria from growing and scale and rust from forming during the recovery operation. These chemicals cannot be discharged to the ocean due to EPA regulations. It would be extremely desirable to treat fluid streams underwater at a floor of a river, lake or ocean, particularly at thousands of feet under sea water, on an ocean floor, to treat, e.g., separate and remove undesirable contaminants and treating chemicals from recovered oil, gas, and/or water process streams.
The apparatus, hereinafter sometimes called “NEMOH™,” and methods described herein are directed to a fluid stream treatment method that can be remotely operated to treat a fluid stream with a reaction or separation media underwater, particularly on the ocean floor, preferably at a depth of at least 500 feet (at a treatment vessel pressure of at least 237 psi), e.g., 1,000 to 10,000 feet at treatment vessel pressures of 455 psi to 4,480 psi, preferably 2,000 to 6,000 feet at treat vessel pressures of 910 psi to 2,696 psi, e.g., filter out contaminants such as water or a chemical additive, such as a corrosion inhibitor, scale inhibitor and/or a preservation fluid from a recovered hydrocarbon or water stream under water, particularly at a depth of thousands of feet under water.